Pairing and Interaction Effects in a Fermionic Quantum Kicked Rotor

The quantum kicked rotor (QKR) is a deceptively simple model that exhibits rich transport phenomena, including a momentum-space analogue of the celebrated Anderson localization effect. While this localization, distinguished by a saturation in energy growth, can occur for kick periods incommensurate with the mass-dependent inverse recoil frequency, resonances and anti-resonances can emerge in the system's energy evolution for commensurate kick periods. The QKR's energy versus kick period "spectrum" thus contains a wealth of information, including how interactions affect resonance shapes and locations. We have measured energy spectra and resonant energy growth in a 6^Li atom-optics realization of the QKR. Using a broad Feshbach resonance, we prepare molecular BECs with tunable contact interactions. Our spectra show a suppression of the main atomic resonance peak and a growth of the main molecular peak as temperature is reduced and pairs form. At our lowest temperatures, we also observe a suppression of the molecular resonance peak and an increased background value away from this resonance as interactions are increased, indicative of interaction-induced dephasing. This dephasing is highlighted further by a decreased rate of resonant energy growth with kick number, as interactions are increased.